Device and method for measuring condensation and/or advance of corrosion

ABSTRACT

A device for measuring condensation and/or advance of corrosion of a conduit includes an insulator extending around the conduit; a first conductor and a second conductor which are arranged such that at least a portion of the insulator lies between the conduit and the first conductor and the second conductor, such that the first conductor forms a first pole of a capacitor, the second conductor forms a second pole of the capacitor, and the portion therebetween comprises a capacitive coupling between the first pole and the second pole. At least one measuring instrument is configured to determine a value which is representative of the capacitive coupling.

The present invention relates to a device and method for measuringcondensation and/or advance of corrosion of a conduit. In addition, theinvention relates to a monitoring controller for use with one or moresuch devices.

For transport of some fluids it is important that these are subject aslittle as possible to thermal losses. The conduits for transporting suchfluids colder than the dew point temperature are therefore typicallythermally insulated. This takes place by enclosing for instancepipelines with insulating shells, optionally provided with a vapourbarrier.

There is however the danger of condensation in such installations.Because the installations are typically exposed to ambient air, and ifthere is a leak in the encasing vapour barrier, the moisture in theambient air can condense onto the conduit at the contact surface withthe inner side of the insulation. The term corrosion under insulation(CUI) is typically used to describe this. Over a period of time suchcondensed moisture can result in corrosion of the conduit, whereby theconduit is damaged (the metal corrodes and the conduit eventually losesits flow efficiency, effectiveness, strength and watertightness). It isdifficult to remove such condensed moisture and replacing a completeinstallation is moreover very expensive. Condensation is therefore bestdetected before the actual corrosion occurs, or in any case as early aspossible, so that a less expensive partial replacement of the insulationis possible.

Known systems for measuring condensation on the conduit and the advanceof corrosion as a result of condensation make use of thermal cameras fordetecting locations with deviating thermal patterns. This solution isnot efficient however because it is expensive and cumbersome and forinstance does not allow detection of heat and/or cold losses in blindspots. The interpretation of such thermal detection is moreoverdifficult; it is not clear whether a heat or cold loss can be attributedto a locally thinner insulation or to a vapour barrier leakage, and avariation is possible due to thermal reflection on a shiny surface.

Further known measuring systems comprise time-domain reflectometrytechniques determining characteristics of electrical lines by observingreflected waveforms. This technique has the disadvantage that thelocation of condensation and/or leakage cannot be accurately detected,especially when condensation and/or leakage occur at different locationsalong the line. These systems still require a user to search forleakages and condensation on conduits through means of thermal cameras.

In order to solve these problems the Belgian patent application BE2014/0429, granted by now as Belgian patent BE 1022693 B9, in the nameof the same applicant as the present patent application, provides adevice for electrically conductive conduits, wherein an insulatorextends around the conduit, and wherein at least one electricalconductor is arranged over, on or in the insulator such that at least aportion of the insulator lies between the conduit and the or eachconductor and such that the conduit forms a first pole of a capacitor,the or each conductor forms a second pole of this capacitor, and theportion therebetween forms part of a dielectric, and wherein at leastone measuring instrument is configured to determine for the or eachconductor a value which is representative of the capacitive action ofthe corresponding capacitor.

In such devices there is however the problem of the conduit having to beelectrically conductive. As a result, such devices cannot be usedwithout question for instance plastic conduits. In such devices there ismoreover a risk of an electrical short-circuit occurring between theconduit and the at least one electrical conductor, for instance at theposition of conduit valves or other protrusions, so that said capacitiveaction is impeded and, as a result, the measurement is no longerworthwhile.

It is an object of the present invention to solve these problems.

The invention provides for this purpose a device for measuringcondensation and/or advance of corrosion of a conduit, comprising: aninsulator extending around the conduit; as well as a first and secondconductor which are arranged such that at least a portion of theinsulator lies between the conduit and the first conductor and thesecond conductor, such that the first conductor forms a first pole of acapacitor, the second conductor forms a second pole of the capacitor,and the portion therebetween comprises a capacitive coupling between thefirst pole and the second pole. The device also comprises at least onemeasuring instrument configured to determine a value which isrepresentative of the capacitive coupling.

This solution allows condensation and/or advance of corrosion to bemeasured with all manner of conduits, which need not necessarily beelectrically conductive, since it is not the conduit itself which isused as second pole of the capacitor but a conductor provided separatelyfor this purpose. For the same reason, the risk of a worthlessmeasurement as a result of an electrical short-circuit between theconduit and one of the two conductors can moreover be reduced becauseeven if one of the two conductors were to make unintended electricalcontact with the conduit, the other of the two conductors keepsfunctioning as reverse pole of the capacitor. The inventiveness of thissolution is based inter alia on the innovative insight of the inventorthat the capacitive action between the first conductor and the secondconductor can be measured more accurately than in the known devicebetween the position of the conductor and the position of the conduit.Tests have shown that in the case of leakage the determined value (inthis case the capacity itself) can change by a factor in the order ofmagnitude of 100 or 1000, while in the case of temperature and humidityfluctuations in the surrounding area only very small changes (in theorder of magnitude of a few percent) occur, which allows condensationand/or advance of corrosion to be measured.

It is an additional advantage of embodiments of the device that thefirst and the second conductor and the measuring instrument can bearranged on an already installed insulator, without electricalconnections still having to be made between the measuring instrument andthe conduit.

According to an embodiment, seen in a longitudinal direction of theconduit, the first and second conductor are arranged at a distance ofeach other or the first and second conductor overlap only partially atan outer end thereof. In this way the capacitive coupling can extendalong a substantial length of the insulator allowing detecting anycondensation or leakage along this length.

A first measuring instrument of said at least one measuring instrumentmay be arranged, typically fixed, on the insulator or on an outer layeron the insulator, between the first and second conductor. For example,there may be arranged an outer layer on the insulator between the firstand the second inductor, and the first measuring instrument may be fixedon the outer layer. The outer layer may be an electrically conductiveouter layer, and this electrically conductive outer layer may begrounded or floating.

According to an embodiment, the device comprises a third conductor whichis arranged such that at least a further portion of the insulator liesbetween the conduit and the second and the third conductor, such thatthe second conductor forms a first pole of a further capacitor, thethird conductor forms a second pole of the further capacitor, and thefurther portion therebetween comprises a further capacitive couplingbetween the first pole and the second pole; wherein the at least onemeasuring instrument is configured to determine a value which isrepresentative for the further capacitive coupling. In this way agreater portion of the insulator can be monitored with the at least onemeasuring instrument.

According to an embodiment, seen in a longitudinal direction of theconduit, the second and third conductor are arranged at a distance ofeach other or the second and third conductor overlap only partially atan outer end thereof.

According to an embodiment, the first conductor extends over a firstlength seen in the longitudinal direction of the conduit, and a surfacearea of the first conductor is at least 10% of a surface area of theconduit along the first length, preferably at least 25%, more preferablyat least 50%. The surface area may also be equal to the surface area ofthe conduit along the first length, or even larger than the surface areaof the conduit along the first length. By increasing the surface area ofthe first and second conductor, the capacitive coupling between of thefirst and second conductor is increased. Hence the accuracy of themeasurement will be increased.

According to an embodiment, the first conductor and the second conductorare each embodied as an electrically conductive coating or cladding forthe insulator. In this way the device can be installed as a whole (withor without the at least one measuring instrument) more simply.

According to an embodiment, the first conductor and the second conductorare each shaped as at least a portion of an electrically conductivesleeve configured to accommodate at least a portion of the insulator. Inthis way the respective poles of the capacitor can cover a large surfacearea and thus have a greater capacity.

According to an embodiment, the at least one measuring instrument can beconfigured to determine a frequency value which is representative of thecapacitive coupling. In this way use can be made of a simplydeterminable parameter for determining the value which is representativeof the capacitive coupling.

According to an embodiment, at least one measuring instrument can beconfigured to drive a variable frequency alternating voltage or currentthrough the capacitive coupling and to measure amplitude and phasechanges thereof. In this way use can be made of simply determinableparameters (amplitude and phase or real and imaginary part of thealternating voltage or current) for the purpose of determining theimpedance value which is representative of the connection. Thisimpedance is frequency-dependent and gives an indication of the advanceof condensation and corrosion.

According to an embodiment, the at least one measuring instrument cancomprise at least one oscillator.

According to an embodiment, the at least one measuring instrument can beintegrated in the insulator. In this way the at least one measuringinstrument is better protected from external influences.

According to an embodiment, the at least one measuring instrument cancomprise at least one of the following power supplies: a wire supply, anenergy yield supply; and a battery supply. A very long lifespan of themeasurement can be obtained with a wire supply, while a battery supplycan be inexpensive and simple to install. An energy yield supply can bevery energy-efficient and autonomous, which can be advantageous in thecase of conduits which are difficult to reach (such as long-distanceconduits).

According to an embodiment, the at least one measuring instrument can beconfigured to transmit the determined value wirelessly to a wirelessreceiver of a monitoring controller, preferably by means ofcommunication technology with low power and far reach (Low-PowerWide-Area Network). In this way the convenience of use can be increased.In addition, central control can be made possible.

According to an embodiment, the first conductor and the second conductorcan be arranged at pitch distance from each other along the insulator.In this way a greater expanse of the conduit can be covered and theaccuracy of the measurement can be increased.

According to an embodiment, the device can comprise a monitoringcontroller which is configured to analyse condensation and/or advance ofcorrosion of the conduit on the basis of the value or values determinedby the or each measuring instrument.

According to an embodiment, the device can comprise at least onetemperature sensor configured to measure a temperature, preferably atthe position of the insulator, and/or at least one moisture sensorconfigured to measure a degree of moisture, wherein the monitoringcontroller is configured during analysis of the condensation and/oradvance of corrosion to take into account the measured temperatureand/or the measured degree of moisture. The temperature sensor and/orthe moisture sensor allow analysis to be performed with greaterprecision.

According to an embodiment, the conduit can be electrically conductiveand the at least one measuring instrument can be configured duringdetermining of the value to take into account the capacitive action of afirst additional capacitor with poles formed by the first conductor andthe conduit, and the capacitive action of a second additional capacitorwith poles formed by the second conductor and the conduit.

In this way the device according to the invention can not only be usedefficiently with electrically non-conductive conduits, but can likewisebe used with conduits which are electrically conductive. In this lattercase the capacitive coupling can advantageously be measured up to aposition deeper in the insulator (i.e. closer to the conduit) since theconduit then forms an electrical contact point between on the one hand afirst additional capacitor formed by the first conductor and the conduitand on the other a second additional capacitor formed by the conduit andthe second capacitor, wherein the insulator in each case serves asrespective dielectric. Such a measurement can be even more effectivewhen the insulator is vapour-tight, since forming condensation is thenable to spread at the position of the conduit.

According to an embodiment, the conduit can be grounded. Alternatively,the conduit can be a floating conduit.

According to an embodiment, a transition area between the firstconductor and the second conductor can comprise a moisture-resistantstrip, preferably butyl tape or rubber. In this way the insulator can bebetter protected against moisture penetrating from outside.

According to an embodiment, at least one of the first conductor and thesecond conductor can be at least partially manufactured from aluminiumor from stainless steel. In this way the device can be moreweather-resistant.

According to an embodiment, at least one of the first and the secondconductor comprises a plurality of interconnected electricallyconductive layer elements. For example, the electrically conductivelayer elements may be elongated elements extending in a longitudinaldirection of the conduit and arranged around the conduit, at a distanceof each other seen in a section perpendicular to the longitudinaldirection. In this way a substantially large surface area of theconductor is achieved while reducing material costs and making thedevice more lightweight such that the mounting of the device is easier.In this way the surface area of the conductor is substantially largerthan the thickness, thereby increasing the capacitive coupling betweenthe first and the second conductor. For example, the plurality ofelectrically conductive elongated elements may be strip like. In otherexemplary embodiment the electrically conductive layers may becylindrical elements arranged at a distance of each other seen in thelongitudinal direction.

In an exemplary embodiment the plurality of interconnected electricallyconductive layer elements are inserted between a first insulation layerand a second insulation layer, wherein in the first and secondinsulation layer together form the insulator. By using a plurality ofinterconnected electrically conductive layer elements instead of acomplete sleeve, the adhesion between the first insulation layer and thesecond insulation layer can be improved.

According to an embodiment, the first and the second conductor areembedded in the insulator. For example, the insulator may comprise afirst insulator layer extending around the conduit and a secondinsulator layer extending around the first insulator, wherein the firstand second conductor are at least partially embedded in the secondinsulator layer. In this way the first and second conductor can beeasily integrated in the insulator and protected against externalinfluences from the environment.

According to an embodiment, the device further comprises connectingmeans between a measuring instrument and the first and second conductor,said connecting means extending from the first and second conductorthrough the insulator to the measuring instrument. In this way themeasuring instrument is easily connected to the conductor therebyreducing the time needed to mount the measuring instrument.

According to an embodiment, the first conductor has a first end and asecond end and the device further comprises a first connector elementextending through the insulator from said first end; and a secondconnector element extending through the insulator from the second end.

The invention further provides a monitoring controller for use with oneor more devices as described above, the monitoring controller beingconfigured to receive one or more values determined by the at least onemeasuring instrument and to analyse condensation and/or advance ofcorrosion of the conduit on the basis of the received value or values.

The skilled person will appreciate that advantages and objectivessimilar to those for the device apply for the corresponding monitoringcontroller, mutatis mutandis.

According to an embodiment, the monitoring controller can comprise awireless receiver which is configured to receive the value or valuesdetermined by the at least one measuring instrument.

The invention further provides a method for measuring condensationand/or advance of corrosion of a conduit. The method comprises ofarranging an insulator around the conduit. The method also comprises ofarranging a first conductor and a second conductor, such that at least aportion of the insulator lies between the conduit and the firstconductor and the second conductor, such that the first conductor formsa first pole of a capacitor, the second conductor forms a second pole ofthe capacitor, and the portion therebetween comprises a capacitivecoupling between the first pole and the second pole. The method alsocomprises of determining a value which is representative of thecapacitive coupling.

The skilled person will appreciate that advantages and objectivessimilar to those for the device apply for the corresponding method,mutatis mutandis.

According to a preferred embodiment, the first and second conductors arearranged at a distance of each other seen in a longitudinal direction ofthe conduit, or such that the first and second conduits overlap onlypartially at an outer end thereof.

According to a preferred embodiment, a third conductor is arranged suchthat at least a further portion of the insulator lies between theconduit and the second and the third conductor, and such that the secondconductor forms a first pole of a further capacitor and the thirdconductor forms a second pole of the further capacitor, and the furtherportion of the insulator comprises a further capacitive coupling betweenthe first pole and the second pole; and a value which is representativefor the further capacitive coupling is determined. Preferably, thesecond and third conductors are arranged at a distance of each other, orsuch that the second and third conductor overlap only partially at anouter end thereof, seen in a longitudinal direction of the conduit.

According to a preferred embodiment, each conductor is provided along afirst length with a surface area which is at least 10% of a surface areaof the conduit along the first length, preferably at least 25%, morepreferably at least 50%. The surface area may also be more or less equalto the surface area of the conduit along the first length, or evenlarger than the surface area of the conduit along the first length.

The length of a conductor may be e.g. between 0.5 m and 10 m, dependingon the type of conduits to be insulated. The diameter of the insulatormay be e.g. between 5 mm and 1200 mm, preferably between 10 mm and 500mm. A distance between the first conductor and the second conductor maybe e.g. between 1 cm and 200 cm, preferably between 2 cm and 150 cm.

According to a preferred embodiment, the method comprises of providingeach of the first conductor and the second conductor as an electricallyconductive coating or cladding for the insulator.

According to a preferred embodiment, the method comprises of providingeach of the first conductor and the second conductor as at least aportion of an electrically conductive sleeve configured to accommodateat least a portion of the insulator.

According to a preferred embodiment, the method of determining the valuecomprises of determining a frequency value which is representative ofthe capacitive coupling.

According to a preferred embodiment, the method comprises of driving avariable frequency alternating voltage or current through the capacitivecoupling and of measuring amplitude and phase changes thereof.

According to a preferred embodiment, the method comprises of integratingat least one measuring instrument in the insulator.

According to a preferred embodiment, the method comprises oftransmitting the determined value wirelessly to a wireless receiver of amonitoring controller, preferably by means of communication technologywith low power and far reach (Low-Power Wide-Area Network).

According to a preferred embodiment, the method comprises of arrangingthe first conductor and the second conductor at pitch distance from eachother along the insulator.

According to a preferred embodiment, the method comprises of analysingcondensation and/or advance of corrosion of the conduit on the basis ofthe determined value or values.

According to a preferred embodiment, the method comprises of measuring atemperature, preferably at the position of the insulator, and/or ofmeasuring a degree of moisture; and analysing the condensation and/oradvance of corrosion while taking into account the measured temperatureand/or the measured degree of moisture.

According to a preferred embodiment, the conduit is electricallyconductive and determining of the value comprises of taking into accountthe capacitive action of a first additional capacitor with poles formedby the first conductor and the conduit, and the capacitive action of asecond additional capacitor with poles formed by the second conductorand the conduit.

According to a preferred embodiment, the method comprises of groundingthe conduit. Alternatively, the method comprises of having the conduitfloat.

According to a preferred embodiment, the method comprises of arranging amoisture-resistant strip, preferably butyl tape or rubber, in atransition area between the first conductor and the second conductor.

According to an exemplary embodiment, the method comprises embedding thefirst and the second conductor in the insulator. For example, a firstinsulator layer may be arranged around the conduit and a secondinsulator layer may be arranged around the first insulator layer,wherein the first and second conductor may be at least partiallyembedded in the second insulator layer or may be inserted between thefirst and the second insulator layer.

According to an exemplary embodiment, the arranging of the first and/orthe second conductor comprises arranging a plurality of interconnectedelectrically conductive elongated elements around the conduit, forexample a plurality of interconnected electrically conductive elongatedelements extending in a longitudinal direction of the conduit andarranged around the conduit, at a distance of each other seen in asection perpendicular to the longitudinal direction.

According to an exemplary embodiment, the determining of a valuecomprises connecting a measuring instrument using connection meansextending from the first and second conductor through the insulator tothe measuring instrument. For example, the method may comprise arranginga first connector element through the insulator to the first conductorand arranging a second connector element through the insulator to thesecond conductor.

The invention further provides a method for analysing condensationand/or advance of corrosion of a conduit, comprising of receiving one ormore values determined according to one of the above described methods;and of analysing the condensation and/or the advance of corrosion of theconduit on the basis of the received value or values.

According to an embodiment, the method comprises of wirelessly receivingthe one or more determined values.

According to another aspect of the invention there is provided a devicefor measuring degradation of a surface layer on a conduit, comprising:an insulator extending around the surface layer on the conduit; a firstconductor and a second conductor at a distance of the first conductor,said first and second conductor being arranged such that at least aportion of the insulator lies between the conduit and the firstconductor and between the conduit and the second conductor; and at leastone measuring instrument configured to determine a value which isrepresentative of the impedance of the surface layer underneath saidportion of the insulator.

According to prior art solutions degradation of a surface layer istypically measured directly on the surface layer using anelectrochemical impedance spectroscopy measurement. In the event ofisolated conduits where the surface layer is not directly accessible, apossibility would be to perform a measurement between the conduit and aconductor arranged around the insulator. However, it has been found thatsuch measurements do not provide accurate results due to external noise.By using a first and a second conductor as specified above, any externalnoise will be present both on the first and the second conductor, andwill be cancelled out as the measurement is a differential measurementperformed between the first and the second conductor.

The at least one measuring instrument may comprise an AC impedancemeasurement apparatus, e.g. an electrochemical impedance spectroscopymeasurement instrument. Using such a measurement, the phase andamplitude of the impedance is obtained in function of the frequency.When the surface layer degrades, the impedance of the surface layerchanges, which causes a change in the phase measurement and a change inthe amplitude measurement.

In addition or alternatively, the at least one measuring instrument maycomprise a DC measurement apparatus, such as a potentiostat or aGalvanostat. For example, a potentiostat measurement will work, when theinsulator is already wet, so that ion transport can take place throughthe insulator and through the surface layer, resulting in a measurementvalue representative for the impedance of the surface layer. Also othermeasurement instruments are possible as long as it is possible todetermine a value which is representative of the degradation of thesurface layer underneath said portion of the insulator. The device mayfurther comprise a monitoring controller which is configured to analysedegradation of the surface layer on the basis of the value or valuesdetermined by the at least one measuring instrument.

The surface layer may be e.g. any one of the following: a coating, acover layer, an oxidation layer. For example, the surface layer may be acorrosion resistant layer, a protective layer, etc.

The surface layer may be a layer which is adhered to the conduit, or maybe a layer which is not adhered to the conduit. e.g. a separate foil.

A thickness of the surface layer is typically smaller than a wallthickness of the conduit. For example, the surface layer may have athickness which is smaller than 10 mm, preferably smaller than 9 mm,more preferably smaller than 8 mm.

According to another aspect of the invention there is provided a methodfor measuring degradation of a surface layer on a conduit, comprising:arranging an insulator around the surface layer on the conduit;arranging a first conductor and a second conductor at a distance of thefirst conductor, such that at least a portion of the insulator liesbetween the conduit and the first conductor and between the conduit andthe second conductor; and determining a value which is representative ofthe impedance of the surface layer underneath said portion of theinsulator. The method may further comprise analysing degradation of thesurface layer on the basis of the determined value or values.

The determining may be done using an AC impedance measurement, such asan electrochemical impedance spectroscopy, or a DC measurement, such asa measurement with a potentiostat or a Galvanostat.

The preferred and exemplary features disclosed above for the device andmethod for measuring condensation and/or advance of corrosion of aconduit may also be present in the device and method for measuringdegradation of a surface layer on a conduit. Also, the devices/methodsmay be combined, i.e. the sane device may be provided with a firstmeasurement instrument to determine a value which is representative ofthe capacitive coupling and a second measuring instrument to determine avalue which is representative of the impedance of the surface layerunderneath said portion of the insulator. Indeed, the same insulator andfirst and second conductor may be used to perform both measurements.When the devices/methods are combined, the first measurement instrumentconfigured to determine a value which is representative of thecapacitive coupling may perform measurements on a regular basis with afirst frequency. The second measuring instrument configured to determinea value which is representative of the impedance of the surface layerwill typically require a more complex measurement which takes longer toperform compared to the duration of the first measurement of a valuewhich is representative of the capacitive coupling. In possibleembodiments, the measurement by the second measuring instrument todetermine a value which is representative of the impedance of thesurface layer, may be performed either on a regular basis but typicallywith a second frequency which is lower than the first frequency, or onan irregular basis, e.g. only when the first measurement by the firstmeasurement instrument indicates leakage or water ingress orcondensation.

According to another aspect of the invention there is provided, aninsulation element, preferably for use in the device or method accordingto any of the embodiments above, comprising an insulator sleeveconfigured for extending around a conduit and having an outer surface; aconductor embedded in the insulator sleeve; at least one connectionelement extending from the conductor through the insulator sleeve to theouter surface thereof. Such insulating elements may be arranged around aconduit, next to each other, seen in a longitudinal direction of theconduit. The connection element allows connecting the conductor to ameasuring instrument or to another conductor of an adjacent insulationelement.

According to an exemplary embodiment, the conductor is shaped as aconductor sleeve having a length which is smaller than a length of theinsulator sleeve and which is fully embedded in the insulator sleeve.According to another embodiment, the conductor comprises a plurality ofinterconnected electrically conductive layer elements, for exampleelongated elements extending in a longitudinal direction of theinsulator sleeve and arranged around the insulator sleeve, at a distanceof each other seen in a section perpendicular to the longitudinaldirection.

According to an exemplary embodiment, the insulator sleeve comprises afirst insulator layer and a second insulator layer. The conductor may bearranged between the first and the second insulator layer, or may beembedded in the second insulator layer.

According to an exemplary embodiment, the insulation element furthercomprising a measuring instrument arranged on or in the insulatorsleeve. The measuring instrument may be configured to transmit ameasured value wirelessly to a wireless receiver of a monitoringcontroller, preferably by means of communication technology with lowpower and far reach (Low-Power Wide-Area Network).

According to an exemplary embodiment, a surface area of the conductor islarger than 10% of the surface area of the outer surface of theinsulator sleeve, preferably larger than 25%, more preferably largerthan 50%.

According to an exemplary embodiment, the conductor is formed as anelectrically conductive coating or cladding.

According to an exemplary embodiment, the insulation element comprisesat least one temperature sensor configured to measure a temperatureand/or at least one moisture sensor configured to measure a degree ofmoisture.

According to an exemplary embodiment, the conductor is at leastpartially manufactured from aluminium or steel, e.g. stainless steel orgalvanised steel.

According to an exemplary embodiment of the insulation element, the atleast one connector element comprises a first connector element arrangedat a first end of the conductor seen in a longitudinal direction of theinsulator sleeve and a second connector element arranged at the otherend of the conductor.

The length of a conductor may be e.g. between 0.5 m and 10 m, dependingon the type of conduits to be insulated. The diameter of the insulatormay be e.g. between 5 mm and 1200 mm, preferably between 10 mm and 500mm.

The invention further relates to an assembly of insulation elements asdescribed above. When arranging insulation elements around a conduit,the conductor of a first insulation element may be electricallyconnected to a conductor of one or two adjacent insulation elements.Also the conductor may be connected to a measuring instrument. Thisallows to form a device as described above in a convenient manner.

The skilled person will appreciate that advantages and objectivessimilar to those for the device apply for the insulation element and theassembly of insulating elements, mutatis mutandis.

The invention will now be further described with reference to anexemplary embodiment shown in the drawing. These exemplary embodimentsare intended for the purpose of a better understanding of the abovedescribed features, advantages and objectives of the invention; they donot limit the invention in any way.

In the drawing:

FIG. 1A is a schematic representation of an embodiment of a deviceaccording to the invention in longitudinal section along thelongitudinal direction of an electrically non-conductive conduit;

FIG. 1B is a schematic representation of another embodiment of a deviceaccording to the invention in longitudinal section along thelongitudinal direction of an electrically conductive conduit:

FIG. 1C is a schematic representation of a part of a first alternativeembodiment of a device according to the invention;

FIG. 1D is a schematic representation of a part of a second alternativeembodiment of a device according to the invention;

FIG. 2 is a schematic representation of an embodiment of an electroniccircuit for use in a measuring instrument according to the invention;

FIG. 3 is a schematic representation of an alternative embodiment of anelectronic circuit for use in a measuring instrument according to theinvention:

FIG. 4 is a schematic representation of another embodiment of anelectronic circuit for use in a measuring instrument according to theinvention.

FIG. 5 is a schematic representation of an embodiment of a device inlongitudinal section along the longitudinal direction of a conduit;

FIG. 6 is a schematic view indicating the capacitive coupling for theembodiment of FIG. 5;

FIG. 7 is a schematic perspective view of an alternative embodiment of adevice;

FIG. 8A-D schematically represent alternative embodiments of a device,illustrating different ways of connecting the measuring instruments:

FIG. 9 is a schematic longitudinal sections of an embodiment of anassembly of insulation elements; and

FIG. 10 is a schematic longitudinal section of an embodiment of aninsulation element;

FIG. 11 illustrates schematically an embodiment of a device fordetermining degradation of a surface layer on a conduit; and

FIGS. 12A and 12B illustrate a measured amplitude and phase in functionof frequency, respectively, for a device with a conduit with an intactsurface layer and with a degraded surface layer.

The same or similar elements are designated in the drawing with the samereference numeral.

FIG. 1A shows a schematic representation of an embodiment of a deviceaccording to the invention in longitudinal section along thelongitudinal direction of an electrically non-conductive conduit. Thefigure shows conduit 1 in cross-section along its longitudinal axis,although the skilled person will appreciate that other embodiments ofthe invention can also be applied in differently shaped conduits.

An insulator 2 extends around conduit 1. Insulator 2 can be configuredfor thermal insulation, but (alternatively or additionally) also foracoustic insulation. Insulator 2 can for instance comprise pre-formedshells which are clamped or fastened around conduit 1, or can forinstance comprise mats which are wrapped around conduit 1. Embodimentsof the invention can be applied with all types and forms of insulator.

In insulator 2 first conductor 3A and second conductor 3B are arrangedsuch that at least a portion of insulator 2 lies between conduit 1 andfirst conductor 3A and second conductor 3B, such that first conductor 3Afirms a first pole of capacitor 4C, second conductor 3B forms a secondpole of capacitor 4C, and the portion therebetween comprises acapacitive coupling between the first pole and the second pole. In otherwords, capacitor 4C has two poles. i.e. first conductor 3A and secondconductor 3B, and the portion of insulator 2 lying between the two polescan serve as (part of) a dielectric for capacitor 4C. The wholecapacitive coupling can then for instance be designated as C, (notshown), as done in FIGS. 2-4.

FIG. 1A further shows measuring instrument 6, which is configured todetermine a value which is representative of the capacitive coupling.Measuring instrument 6 can for this purpose be connected respectively tofirst conductor 3A by means of first connection 6A and to secondconductor 3B by means of second connection 6B. The skilled person willappreciate that measuring instrument 6 is shown schematically in theembodiment shown in the figure, and that all manner of practicalembodiments can be opted for, depending on the practical situation.

In some embodiments measuring instrument 6 can transmit the determinedvalue preferably wirelessly to (a wireless receiver of) a monitoringcontroller (not shown) for use with one or more devices according to theinvention. The monitoring controller can be configured to receive one ormore values determined by measuring instrument 6 and to analysecondensation and/or advance of corrosion of conduit 1 on the basis ofthe received value or values. If wireless communication is used, thiscan for instance be done by means of communication technology with lowpower and far reach (Low-Power Wide-Area Network). Examples hereof are;LoRa/LoRaWAN, SigFox, Bluetooth (LE). Alternatively, use can also bemade of communication technology with a relatively higher power, such aswireless local network technology (Wireless Local Area Network, WLAN,such as Wi-Fi, i.e. IEEE 802.11) or mobile cellular network technology(such as GSM and related standards and protocols).

FIG. 1A also shows optional strip 5 which covers an area of insulator 2lying in a transition area between first conductor 3A and secondconductor 3B. In this context a transition area can comprise an area orspace lying between edges and/or walls of outer ends of first conductor3A and second conductor 3B. Strip 5 is advantageously moisture-resistantin order to impede moisture penetrating from outside. In preferredembodiments it is possible to opt for butyl tape or rubber. It isadvantageous for strip 5 also to cover a sufficiently wide part (forinstance at least 1 cm, preferably at least 5 cm) of respective outerends of first conductor 3A and second conductor 3B in order to obtain abetter operation.

According to alternative embodiments, first conductor 3A and secondconductor 3B can be integrated in a coating or cladding of insulator 2.This has the advantage that the device can be installed as a whole,which requires fewer operational steps.

In a specific embodiment (as shown here) first conductor 3A and secondconductor 3B are each shaped as at least a portion of an electricallyconductive sleeve which is configured to accommodate at least a portionof insulator 2. This has the advantage that each of the conductors cancover a greater surface area than in some other forms (such as cords orelongate plates), so that the capacity can also be greater.

In some embodiments measuring instrument 6 can be powered by means of apotential 30 wire (not shown). This has the advantage that themeasurement can be more accurate. In other embodiments measuringinstrument 6 can be powered by means of a battery (not shown). This hasthe advantage that it is cheaper and that installation is easier. In apreferred embodiment the two options can be combined, and it is forinstance possible to first use a battery supply over short segments inthe short term for general detection of whether there is a risk ofcondensation and/or advance of corrosion, and then, after detectionthereof, to continue with a wire supply in the longer term in order tomeasure more accurately.

FIG. 1B show a schematic representation of another embodiment of adevice according to the invention in a longitudinal section along thelongitudinal direction of an electrically conductive conduit. The figureshows first additional capacitor 4A and second additional capacitor 4B.These additional capacitors are optional in the sense that it is usefulto base the determination of the value partly thereon when conduit 1 iselectrically conductive, as is the case in this figure. This has theadvantage that moisture and/or corrosion can be measured with moreprecision up to a position deeper in insulator 2 (i.e. closer to conduit1) since electrically conductive conduit 1 is there capacitively active.

In this other embodiment the capacitive coupling can be deemed theparallel circuit of capacitor 4C on the one hand and the serial circuitof first additional capacitor 4A and second additional capacitor 4B onthe other. The whole capacitive coupling can then for instance bedesignated as C, (not shown), as done in FIGS. 2-4.

FIG. 1C shows a schematic representation of a part of a firstalternative embodiment of a device according to the invention. Thefigure shows particularly a cross-section of the part of the devicewhere first conductor 3A and second conductor 3B are situated close toeach other. In this first alternative embodiment of the device firstconductor 3A and second conductor 3B are arranged overlapping at leastpartially at their respective outer ends, wherein electricallyinsulating strip 5 extends in a transition area between first conductor3A and second conductor 3B over an area at least the same size as theoverlap in order to prevent direct electrical conduction between firstconductor 3A and second conductor 3B. Strip 5 can for instance bemanufactured from rubber, which has good electrically insulatingproperties and moreover has good moisture resistance.

FIG. 1D shows a schematic representation of a part of a secondalternative embodiment of a device according to the invention. Thissecond alternative embodiment differs from the first alternativeembodiment shown in FIG. 1C in that the outer ends of first conductor 3Aand second conductor 3B are formed in complementary manner (in thisexample as two mutually engaging hooks) in order to hold the strip 5lying therebetween more firmly.

FIG. 2 shows a schematic representation of an embodiment of anelectronic circuit 10 for use in a measuring instrument according to theinvention, for instance measuring instrument 6 of FIG. 1A.

Circuit 10 is powered via terminal V_(CC), where during operation avoltage level can be supplied as power supply, this also beingdesignated as V_(CC)—this voltage level can for instance lie between 3and 15 volt. Circuit 10 comprises integrated circuit (IC) 11, which ishere used to determine time intervals (a timer integrated circuit orIC), for instance on the basis of a 555 IC as developed by Signetics.The skilled person will appreciate that all manner of electroniccomponents can alternatively be used, but that this present embodimentis practical since it makes use of standard components.

The power supply is supplied to IC 11 in terminal 8 (V_(CC)) and is alsoused to control terminal 4 with negative reset function (┌RESET). Ifterminal 4 is grounded, IC 11 is reset.

The power supply runs over resistance R1 and is further connected toterminal 7 (DIS) of IC 11, which functions as open collector. Fromthere, the remaining voltage runs further over resistance R2 and isfurther connected to terminal 6 (THR) and terminal 2 (TRIG) of IC 11,which can be used during operation to determine the start and end of thetime interval.

From resistance R2, the remaining voltage runs over capacitor C_(eq) toground (GN)). Capacitor C_(eq) can be seen as only capacitor 4C if theconduit is electrically non-conductive, or as the parallel circuit of onthe one hand capacitor 4C and on the other the serial circuit of firstadditional capacitor 4A and second additional capacitor 4B if theconduit is electrically conductive.

The grounding is also connected to terminal 1 (GND) of IC 11, and viacapacitor 13, preferably with a low capacity, for instance 10 nF, toterminal 5 (CTRL) of IC 11. Terminal 1 can be used during operation tofunction as ground reference voltage (for instance 0 volt). Terminal 5can be used during operation to provide control access to an internalvoltage divider in IC 11 in order to (indirectly) control the durationof the time interval.

Output signal 12 (Out) is supplied via terminal 3 (OUT) of IC 11. Duringoperation output signal 12 takes the form of a continuous current ofrectangular voltage pulses, this current having a certain frequency(f_(Out)). This frequency f_(Out) can be determined as follows:f_(Out)=(C_(eq)·(R1+2 R2)·ln(2)).

With this configuration circuit 10 can function as a stablemultivibrator. i.e. as electronic oscillator, which produces a frequencyvalue f_(Out) which is representative of the capacitive action of thedevice as discussed for FIG. 1A. If desired, the frequency value f_(Out)can optionally also be converted to a capacity expressed in farad, forinstance using a microcontroller (not shown), although the skilledperson will appreciate that this additional step is not a necessity inbeing able to approximate the capacitive action of the capacitor(s). Theskilled person will furthermore appreciate that many otherconfigurations of a measuring instrument are possible. For example, themeasurement instrument may be configured to generate a waveform, such asa sinusoidal or square waveform, and to measure a response.

FIG. 3 shows a schematic representation of an alternative embodiment ofan electronic circuit 20 for use in a measuring instrument according tothe invention, for instance measuring instrument 6 of FIG. 1A.

Circuit 20 comprises opamp 21 and comparator 22. The output terminal ofopamp 21 is connected in series to capacitor C_(eq) with similarobservations as made above with reference to FIG. 2. Capacitor C_(eq) isconnected to the negative input terminal of opamp 21. Capacitor C_(eq)is also connected via resistance R1 to the output terminal of comparator22. In addition, capacitor C_(eq) is connected via resistance R3 to thepositive input terminal of comparator 22, which in turn is connected viaresistance R2 to the output terminal of comparator 22. The positiveinput terminal of opamp 21 is connected via resistance R4 to thenegative input terminal of comparator 22. The output terminal ofcomparator 22 produces output signal 23 (Out). This output signal 23 canbe used in similar manner as output signal 12 in FIG. 2, since they areboth pulses.

FIG. 4 shows a schematic representation of another embodiment of anelectronic circuit 40 for use in a measuring instrument according to theinvention, for instance measuring instrument 6 of FIG. 1A.

Circuit 40 comprises integrated circuit (IC) 48 with terminals 45, 46and 47. First pole 41 of the capacitor is coupled to input terminal 47.First pole 41 is coupled to second pole 42 of the capacitor overcapacitive coupling 44. Source 43 drives a variable frequencyalternating voltage or alternating current through capacitive coupling44. IC 48 measures amplitude changes (for instance at output terminal45) and/or phase changes (for instance at output terminal 46),particularly phase shifts, thereof.

FIG. 5 shows a schematic representation of another embodiment of adevice for measuring condensation and/or advance of corrosion of aconduit 1. The device comprises an insulator 2 extending around theconduit, a first conductor 3A, a second conductor 3B, and a thirdconductor 3C. The first and second conductor 3A, 3B are arranged suchthat at least a portion of the insulator 2 lies between the conduit 1and the first conductor 3A and the second conductor 3B, such that thefirst conductor 3A forms a first pole of a capacitor 4, the secondconductor 3B forms a second pole of the capacitor 4. The third conductor3C is arranged such that at least a further portion of the insulator 2lies between the conduit and the second and the third conductor 3B, 3Cand such that the second conductor 3B forms a first pole of a furthercapacitor 4, the third conductor 3C forms a second pole of the furthercapacitor 4, and the further portion of the insulator 2 comprises afurther capacitive coupling between the first pole and the second poleof capacitor 4. Seen in a longitudinal direction of the conduit, thefirst, second and third conductors 3A, 3B, 3C are arranged at a distanceof each other.

The device further comprises a plurality of measuring instruments 6configured to determine a value which is representative of thecapacitive coupling between adjacent conductors 3A, 3B, 3C. A firstmeasuring instrument 6 may be connected between first conductor 3A andsecond conductor 3B, a second measuring instrument 6 may be connectedbetween second conductor 3B and third conductor 3C, etc. Between thefirst and the second conductor 3A, 3B an intermediate outer layer 31,e.g. an electrically conductive intermediate layer, may be arrangedaround the insulator 2. This electrically conductive outer layer 31 maybe grounded or floating. Similar intermediate outer layers 31 may bearranged between the other adjacent conductors 3B, 3C, etc. Theintermediate conductive layer may serve as a support for a measuringinstrument 6. Preferably, each conductor 3A, 3B, 3C extends over a firstlength L seen in the longitudinal direction, and a surface area of eachconductor is at least 10% of a surface area of the conduit 1 along thefirst length, preferably at least 25%, more preferably at least 50%. Itis noted that the conductors 3A. 3B. 3C may also extend over differentlengths. The conductor 3A. 3B. 3C may be formed as a sleeve, such thatthe surface area will be even more than the surface are of the conduitalong length L. However, in order to save material, the conductor 3A,3B, 3C may be formed as a plurality of interconnected conductive layerelements, see also the example of FIG. 6. Although not shown in FIG. 5,a strip 5 which covers an area of the insulator 2 may be arrangedbetween the first conductor 3A and the intermediate layer 31 and betweenthe intermediate layer 31 and the second conductor 3B, similar to whathas been illustrated and described in FIGS. 1A and 1B. Such a device hasthe advantage that with a relatively small amount of simple measuringinstruments 6 a large section of piping may be monitored. Though notshown on the figures it will be clear to the skilled person that theintermediate layer 31 and the conduit 1 may be grounded or floating, ora combination of grounded and floating may be used depending on thesituation. It is noted that the capacitive coupling between the firstand the second conductor 3A, 3B may comprise a series/parallelconnection of a plurality of “capacitors” 4A-4F to result in anequivalent capacitance C_(eq) (corresponding with capacitor 4 in FIG.5). This is illustrated in FIG. 6 where it is assumed that theintermediate layer 31 and the conduit 1 are made of an electricallyconductive material.

The length L1 of a conductor 3A, 3B, 3C may be e.g. between 0.5 m and 10m, depending on the type of conduits to be insulated. The diameter ofthe insulator may be e.g. between 5 mm and 1200 mm, preferably between10 mm and 500 mm. The distance d between the first conductor 3A and thesecond conductor 3B may be e.g. between 1 cm and 200 cm, preferablybetween 2 cm and 150 cm.

FIG. 7 illustrates an embodiment of a device comprising a plurality ofinsulator segments 2A. 2B, etc. The insulator segments 2A, 2B, alsocalled insulation elements form together the insulator of the device.The insulator segments 2A, 2B extend around a conduit 1. A firstconductor consisting of a plurality of interconnected electricallyconductive layer elements 3A′ and a second conductor consisting of aplurality of interconnected electrically conductive layer elements 3B′are arranged on or in the first insulator segment 2A and the secondinsulator segment 2B, respectively. The electrically conductive layerelements 3A′. 3B′ may be elongated strip-like elements extending in alongitudinal direction of the conduit 1 and arranged around the conduit1, at a distance of each other seen in a section perpendicular to thelongitudinal direction. Preferably, each conductor extends over a firstlength L1 seen in the longitudinal direction, and a total surface areaof each conductor (i.e. of all strips 3A′ or 3B′) is at least 10% of asurface area of the conduit 1 along the first length, preferably atleast 25%, more preferably at least 50%. A measuring instrument 6 may beconnected between the first conductor 3A′ and the second conductor 3B′.The space between insulator segments 2A, 2B may be filled with aninsulating glue or paste. Further, any features disclosed above forother embodiments may also be applicable in the embodiment of FIG. 7.

FIGS. 8A-8D) illustrates different possible embodiments for performingthe measurements. In the embodiment of FIG. 8A, a plurality ofconductors 3A-3F are arranged next to each other on or in an insulator 2arranged around a conduit 1 with an axis A. A first measuring instrument6 is connected between the first conductor 3A and the third conductor3C, a second measuring instrument 6 is connected between the secondconductor 3B and the fourth conductor 3D, a third measuring instrument 6is connected between the third conductor 3C and the fifth conductor 3E,etc. Such a set-up can provide a high accuracy. Indeed, e.g. a leakageunderneath conductor 3C can be detected both by the first and the thirdmeasuring instrument 6. The embodiment of FIG. 8B is similar to theembodiment of FIG. 6, but the intermediate conductive layers 31 have thesame length as the conductors 3A, 3B, 3C. In the embodiment of FIG. 5C,no intermediate unconnected layers are present, and each pair ofadjacent conductors 3A, 3B; 3B, 3C; 3C, 3D; etc. is connected to ameasuring instrument 6. In the embodiment of FIG. 8D, the conductors 3A,3B, 3C, etc. are arranged at different distances from the conduit 1. Forexample, conductors 3A, 3C 3E may be arranged between a first and asecond insulation layer of the insulator 2, whilst conductors 3B and 3Dare arranged on an outer surface of the insulator. Optionally themeasuring instruments 6 may also be arranged on the outer surface of theinsulator 2. In an alternative embodiment all conductors 3A-3E may bearranged between a first and a second insulation layer of the insulator2. More generally, in the embodiments of FIGS. 8A-8D all or someconductors 3A, 3B, etc. may be embedded in the insulator 2.

FIG. 9 illustrates an embodiment of an assembly of insulation elements100A, 100B, 100C, 100D, 100E. Each insulation element 100A-E comprisesan insulator sleeve 2A-2E configured for extending around a conduit 1, aconductor 3A-3E embedded in the insulator sleeve 2A-2E, and at least oneconnection element 103, 104 extending from the conductor 3A-3E throughthe insulator sleeve 2A-2E to the outer surface thereof. The conductor3A-3E may be shaped as a conductor sleeve having a length L1 which issmaller than a length Li of the insulator sleeve 2A-2E and may be fullyembedded in the insulator sleeve 2A-2E. In an alternative embodiment,the conductor 3A-3E may comprises a plurality of interconnectedelectrically conductive layer elements. e.g. as disclosed in connectionwith FIG. 7, wherein the plurality of interconnected electricallyconductive layer elements are embedded in the insulator sleeve 2A-2E.The insulator sleeve 2A-2E may comprise a first insulator layer 101 anda second insulator layer 102, and the conductor 3A-3E may be arrangedbetween the first insulator layer 101 and the second insulator layer102. By using a plurality of interconnected electrically conductivelayer elements instead of a complete sleeve for the conductors 3A-3E,the adhesion between the first insulation layer 101 and the secondinsulation layer 102 can be improved.

A measuring instrument 6 may be arranged on the insulator sleeve 2D, asshown for insulating element 100D. The measurement instrument 6 may beconnected to conductors 3C, 3E of adjacent insulation elements 100C,100E as shown, but could also be connected the conductor of theinsulation element in which it is included (not shown in FIG. 9). Themeasuring instrument 106 may be configured to transmit a measured valuewirelessly to a wireless receiver of a monitoring controller. To allowfor an easy connection, for each insulation element 100A-E, connectorelements 103, 104 pass from the outer surface of the insulator 2A-2E tothe conductor 3A-3E. In the illustrated embodiment two connectorelements 103, 104 are provided, one at each end of the conductor 3A-3E,but it is also possible to provide only one connector element or toprovide more than two connector elements. The connector elements 103,104 can be used to interconnect adjacent conductors. For example,conductor 3A is electrically connected to conductor 3B through connectorelement 104 of insulation element 100A, a connecting wire 110, andconnector element 103 of insulation element 100B.

FIG. 10 illustrates another embodiment of an insulation element 100. Theinsulation element 100 comprises an insulator sleeve 2 configured forextending around a conduit 1, a first conductor 3A and a secondconductor 3B both embedded in the same insulator sleeve 2, and aplurality of connection elements 103, 104, 105, 106 extending from thefirst and second conductor 3A, 3B through the insulator sleeve 2 to theouter surface thereof. The conductors 3A, 3B may be shaped as conductorsleeves at a distance d of each other, see in the axial direction, andmay be fully embedded in the insulator sleeve 2. In an alternativeembodiment, the conductors 3A, 3B may comprise a plurality ofinterconnected electrically conductive layer elements, e.g. as disclosedin connection with FIG. 7, wherein the plurality of interconnectedelectrically conductive layer elements are embedded in the insulatorsleeve 2. The insulator sleeve 2 may comprise a first insulator layer101 and a second insulator layer 102, and the conductors 3A. 3B may bearranged between the first insulator layer 101 and the second insulatorlayer 102.

A measuring instrument 6 may be arranged on the insulator sleeve 2. Themeasurement instrument 6 may be connected between the first and secondconductors 3A, 3B, as shown, but could also be connected to a conductorof an adjacent insulation element. The measuring instrument 106 may beconfigured to transmit a measured value wirelessly to a wirelessreceiver of a monitoring controller. To allow for an easy connection,connector elements 103, 104, 105, 106 pass from the conductors 3A, 3Bthrough second insulation layer 102. In the illustrated embodiment, perconductor, two connector elements are provided, one at each end of theconductor 3A, 3B, hut it is also possible to provide only one connectorelement or to provide more than two connector elements per conductor 3A.3B. The connector elements 105, 106 can be connected to a measuringinstrument 6, and the other connector elements 103, 104 can be used forinterconnecting adjacent insulation elements 100.

FIG. 11 illustrates an embodiment of a device and method for measuringdegradation of a surface layer 200 on a conduit 1. The surface layer 200can be a coating, a cover layer, an oxidation layer, etc. Typically thesurface layer has a thickness ts which is smaller than the thickness tcof the wall of the conduit 1. For example, the surface layer 200 mayhave a thickness ts which is smaller than 10 mm, preferably smaller than9 mm, more preferably smaller than 8 mm. The thickness ts of the surfacelayer 200 may also be of the order of microns, e.g. of the order of 100microns. The thickness ti of the insulator may be e.g. between 5 mm and500 mm, preferably between 9 mm and 250 mm. For example, the surfacelayer may be a corrosion resistant surface layer or another protectivesurface layer, such as a cathodic protection. The device comprises aninsulator 2 extending around the surface layer 200 on the conduit 1, afirst conductor 3A and a second conductor 3B at a distance of the firstconductor, said first and second conductor 3A, 3B being arranged suchthat at least a portion of the insulator lies between the conduit andthe first conductor and between the conduit and the second conductor;and a measuring instrument 6 configured to determine a value which isrepresentative of the impedance 204C of the surface layer underneathsaid portion of the insulator 2. By using a first and a second conductor3A, 3B as specified above, any external noise will be present both onthe first and the second conductor, and will be cancelled out as themeasurement is a differential measurement performed between the firstand the second conductor 3A, 3B.

The measuring instrument 6 may comprise an electrochemical impedancespectroscopy measurement instrument or any other AC impedancemeasurement. Using such a measurement, the phase and amplitude of theimpedance is obtained in function of the frequency. When the surfacelayer 200 degrades, the impedance 204C of the surface layer changes,which causes a change in the phase measurement and a change in theamplitude measurement. This is illustrated in FIGS. 12A and 12B. FIG.12A illustrates schematically a measured curve 1203 for the phasewithout degradation and a curve 1204 for the phase with degradation,illustrating a change of the phase curve due to a degradation of thesurface layer 200. FIG. 12B illustrates schematically a measured curve1201 for the amplitude without degradation and a curve 1202 for theamplitude with degradation, illustrating a decrease of the amplitude dueto a degradation of the surface layer 200. Also other AC or DCmeasurement instruments are possible as long as it is possible todetermine a value which is representative of the impedance 204C of thesurface layer 200 underneath said portion of the insulator 2. The otherimpedances 104A, 104B, 204A, 204B, 104C (shown in a simplified model inFIG. 11) will also influence the measurements, but a change of themeasured value of values will be representative of a degradation of thesurface layer. The device may further comprise a monitoring controllerwhich is configured to analyse degradation of the surface layer on thebasis of the value or values determined by the measuring instrument 6.

The preferred and exemplary features disclosed above for the device andmethod for measuring condensation and/or advance of corrosion of aconduit may also be present in the device and method for measuringdegradation of a surface layer on a conduit. More in particular, thedevices of FIGS. 1-10 may also be used for measuring degradation of asurface layer on a conduit when a suitable measuring instrument 6 ischosen. Also, the devices/methods may be combined, i.e. the same devicemay be provided with a first measurement instrument 6 to determine avalue which is representative of the capacitive coupling 4C illustratedin FIG. 1A and a second measuring instrument 6 to determine a valuewhich is representative of the impedance 204C of the surface layerunderneath said portion of the insulator 2. Indeed, the same insulator 2and first and second conductor 3A. 3B may be used to perform bothmeasurements.

In the embodiments of FIGS. 5 and 11 the intermediate layer 31 may beused to mount one or more measurement instruments 6 and/or one or morepower supplies for feeding the one or more measuring instruments 6.Further this intermediate layer 31 may be used to mount a support forfixing the conduit 1 with insulator 2 to a wall. However, it is alsopossible to use a set-up without an intermediate layer, e.g. as shown inFIGS. 1A-1B and 9.

The skilled person will understand that many modifications and variantscan be envisaged within the scope of the invention, which is definedsolely by the following claims.

1. Device for measuring condensation and/or advance of corrosion of aconduit (1), comprising: an insulator (2) extending around the conduit;a first conductor (3A) and a second conductor (3B) which are arrangedsuch that at least a portion of the insulator lies between the conduitand the first conductor and the second conductor, such that the firstconductor forms a first pole of a capacitor (4C), the second conductorforms a second pole of the capacitor, and the portion therebetweencomprises a capacitive coupling between the first pole and the secondpole; and at least one measuring instrument (6) configured to determinea value which is representative of the capacitive coupling.
 2. Deviceaccording to claim 1, wherein the first conductor and the secondconductor are each embodied as an electrically conductive coating orcladding for the insulator.
 3. Device according to any one of theforegoing claims, wherein the first conductor and the second conductorare each shaped as at least a portion of an electrically conductivesleeve configured to accommodate at least a portion of the insulator. 4.Device according to any one of the foregoing claims, wherein the atleast one measuring instrument is configured to determine a frequencyvalue which is representative of the capacitive coupling.
 5. Deviceaccording to any one of the foregoing claims, wherein the at least onemeasuring instrument is configured to drive a variable frequencyalternating voltage or current through the capacitive coupling and tomeasure amplitude and phase changes thereof.
 6. Device according to anyone of the foregoing claims, wherein the at least one measuringinstrument comprises at least one oscillator.
 7. Device for measuringdegradation of a surface layer on a conduit (1), comprising: aninsulator (2) extending around the surface layer on the conduit; a firstconductor (3A) and a second conductor (3B) at a distance of the firstconductor, said first and second conductor being arranged such that atleast a portion of the insulator lies between the conduit and the firstconductor and between the conduit and the second conductor; and at leastone measuring instrument (6) configured to determine a value which isrepresentative of the impedance of the surface layer underneath saidportion of the insulator.
 8. Device according to the previous claim,wherein the at least one measuring instrument comprises anelectrochemical impedance spectroscopy measurement instrument.
 9. Deviceaccording to claim 7 or 8, wherein the at least one measuring instrumentcomprises a DC measurement apparatus.
 10. Device according to any one ofthe claims 7-9, comprising a monitoring controller which is configuredto analyse degradation of the surface layer on the basis of the value orvalues determined by the at least one measuring instrument.
 11. Deviceaccording to any one of the claims 7-10, wherein the surface layer isany one of the following: a coating, a cover layer, an oxidation layer.12. Device according to any one of the previous claims, wherein, seen ina longitudinal direction of the conduit, the first and second conductor(3A, 3B) are arranged at a distance of each other; or wherein, seen inan axial direction of the conduit, the first and second conductoroverlap only partially at outer ends thereof with insulation materialpresent between the outer ends.
 13. Device according to any one of theforegoing claims, wherein a first measuring instrument of said at leastone measuring instrument is fixed on or in the insulator or on an outerlayer (31) on the insulator.
 14. Device according to any one of theforegoing claims, comprising a third conductor (3C) which is arrangedsuch that at least a further portion of the insulator (2) lies betweenthe conduit and the second conductor (3B) and between the conduit andthe third conductor (3C); wherein the at least one measuring instrumentis configured to perform a measurement between the second and the thirdconductor.
 15. Device according to any one of the foregoing claims,wherein the first conductor extends over a first length seen in thelongitudinal direction, and wherein a surface area of the firstconductor is at least 10% of a surface area of the conduit along thefirst length, preferably at least 25%, more preferably at least 50%. 16.Device according to any one of the foregoing claims, wherein the atleast one measuring instrument is integrated in the insulator. 17.Device according to any one of the foregoing claims, wherein the atleast one measuring instrument comprises at least one of the followingpower supplies: a wire supply, an energy yield supply; and a batterysupply.
 18. Device according to any one of the foregoing claims, whereinthe at least one measuring instrument is configured to transmit thedetermined value wirelessly to a wireless receiver of a monitoringcontroller, preferably by means of communication technology with lowpower and far reach (Low-Power Wide-Area Network).
 19. Device accordingto any one of the foregoing claims, wherein the first conductor and thesecond conductor are arranged at pitch distance from each other alongthe insulator, seen in a longitudinal direction of the conduit. 20.Device according to claim 1, optionally in combination with any one ofthe claims 2-6 and 11-19, comprising a monitoring controller which isconfigured to analyse condensation and/or advance of corrosion of theconduit on the basis of the value or values determined by the or eachmeasuring instrument.
 21. Device according to claim 10 or 20, comprisingat least one temperature sensor configured to measure a temperature,preferably at the position of the insulator, and/or at least onemoisture sensor configured to measure a degree of moisture; wherein themonitoring controller is configured during analysis of the condensationand/or advance of corrosion to take into account the measuredtemperature and/or the measured degree of moisture.
 22. Device accordingto the previous claim, wherein the temperature sensor comprises aplurality of power supplies.
 23. Device according to any one of theforegoing claims, wherein the conduit is electrically conductive. 24.Device according to the previous claim, wherein the conduit is groundedor floating.
 25. Device according to any one of the foregoing claims,wherein a transition area between the first conductor and the secondconductor comprises a moisture-resistant strip, preferably butyl tape orrubber.
 26. Device according to any one of the foregoing claims, whereinat least one of the first conductor and the second conductor is at leastpartially manufactured from aluminium or from stainless steel. 27.Device according to any one of the foregoing claims, wherein at leastone of the first and the second conductor comprises a plurality ofinterconnected electrically conductive layer elements (3A′; 3B′). 28.Device according to the previous claim, wherein the plurality ofelectrically conductive layer elements are strip like.
 29. Deviceaccording to any one of the previous claims, wherein the first and thesecond conductor are embedded in the insulator.
 30. Device according toany one of the previous claims, further comprising connecting meansbetween a first measuring instrument of the at least one measuringinstrument and the first and second conductor, said connecting meansextending from the first and second conductor through the insulator tothe first measuring instrument.
 31. Device according to the previousclaim, wherein the first conductor has a first end and a second end andwherein the device further comprises a first connector element extendingthrough the insulator from said first end; and a second connectorelement extending through the insulator from the second end. 32.Monitoring controller for use with one or more devices according to anyone of the foregoing claims, the monitoring controller being configuredto receive one or more values determined by the at least one measuringinstrument and to analyse condensation and/or advance of corrosion ofthe conduit on the basis of the received value or values and/or and toanalyse degradation of a surface layer on the conduit on the basis ofthe received value or values.
 33. Monitoring controller according toclaim 32, comprising a wireless receiver which is configured to receivethe value or values determined by the at least one measuring instrument.34. Method for measuring condensation and/or advance of corrosion of aconduit, comprising of: arranging an insulator around the conduit;arranging a first conductor and a second conductor, such that at least aportion of the insulator lies between the conduit and the firstconductor and the second conductor, such that the first conductor formsa first pole of a capacitor, the second conductor forms a second pole ofthe capacitor, and the portion therebetween comprises a capacitivecoupling between the first pole and the second pole; and determining avalue which is representative of the capacitive coupling.
 35. Methodaccording to claim 34, comprising of providing each of the firstconductor and the second conductor as an electrically conductive coatingor cladding for the insulator.
 36. Method according to any one of theclaims 34-35, comprising of providing each of the first conductor andthe second conductor as at least a portion of an electrically conductivesleeve configured to accommodate at least a portion of the insulator.37. Method according to any one of the claims 34-36, wherein determiningthe value comprises of determining a frequency value which isrepresentative of the capacitive coupling.
 38. Method according to anyone of the claims 34-37, comprising of driving a variable frequencyalternating voltage or current through the capacitive coupling and ofmeasuring amplitude and phase changes thereof.
 39. Method according toany one of the claims 34-38, comprising of analysing condensation and/oradvance of corrosion of the conduit on the basis of the determined valueor values.
 40. Method for measuring degradation of a surface layer on aconduit (1), comprising: arranging an insulator (2) around the surfacelayer on the conduit; arranging a first conductor (3A) and a secondconductor (3B) at a distance of the first conductor, such that at leasta portion of the insulator lies between the conduit and the firstconductor and between the conduit and the second conductor; anddetermining a value which is representative or the impedance of thesurface layer underneath said portion of the insulator.
 41. Methodaccording to claim 40, wherein the determining is done usingelectrochemical impedance spectroscopy.
 42. Method according to claim 40or 41, wherein the determining comprises performing a DC measurement,e.g. using a potentiostat or a Galvanostat.
 43. Method according to anyone of the claims 40-42, comprising analysing degradation of the surfacelayer on the basis of the determined value or values determined. 44.Method according to any one of the claims 34-43, wherein the arrangingof the first and second conductor comprises the arranging of the firstand second conductor at a distance of each other, seen in a longitudinaldirection of the conduit; or such that, seen in a longitudinal directionof the conduit, the first and second conduit overlap only partially atan outer end thereof.
 45. Method according to any one of the claims34-44, comprising of transmitting the determined value wirelessly to awireless receiver of a monitoring controller, preferably by means ofcommunication technology with low power and far reach (Low-PowerWide-Area Network).
 46. Method according to any one of the claims 34-45,comprising of arranging the first conductor and the second conductor atpitch distance from each other along the insulator.
 47. Method accordingto any one of the claims 34-46, comprising of measuring a temperature,preferably at the position of the insulator, and/or of measuring adegree of moisture; and analysing the condensation and/or advance ofcorrosion while taking into account the measured temperature and/or themeasured degree of moisture.
 48. Method according to any one of theclaims 34-47, wherein the conduit is electrically conductive.
 49. Methodaccording to the previous claim, comprising of grounding the conduit orof having the conduit float.
 50. Method according to any one of theclaims 34-49, comprising of arranging a moisture-resistant strip,preferably butyl tape or rubber, in a transition area between the firstconductor and the second conductor.
 51. Method according to any one ofthe claims 34-50, comprising of embedding the first and the secondconductor in the insulator.
 52. Method according to any one of theclaims 34-51, wherein the arranging of the first conductor comprisesarranging a plurality of interconnected electrically conductiveelongated elements (3A′; 3B′) around the conduit.
 53. Method accordingto any one of the claims 34-52, wherein the determining of a valuecomprises connecting a measuring instrument using connection meansextending from the first and second conductor through the insulator. 54.Method for analysing condensation and/or advance of corrosion of aconduit and/or degradation of a surface layer on the conduit, comprisingof: receiving one or more values determined according to the methodaccording to any one of the claims 34-53; and analysing the condensationand/or the advance of corrosion of the conduit and/or the degradation ofthe surface layer of the conduit on the basis of the received value orvalues.
 55. Method according to the previous claim, comprising ofwirelessly receiving the one or more determined values.
 56. Insulationelement, preferably for use in a device according to any of the claims1-31 or in a method according to any one of the claims 34-55,comprising: an insulator sleeve configured for extending around aconduit and having an outer surface; a conductor embedded in theinsulator sleeve; at least one connection element extending from theconductor through the insulator sleeve to the outer surface thereof. 57.Insulation element according to the previous claim, wherein theconductor is shaped as a conductor sleeve having a length which issmaller than a length of the insulator sleeve and which is fullyembedded in the insulator sleeve.
 58. Insulation element according toclaim 56, wherein the conductor comprises a plurality of interconnectedelectrically conductive layer elements (3A′; 3B′).
 59. Insulationelement according to any one of the claims 56-58, wherein the insulatorsleeve comprises a first insulator layer and a second insulator layer,and wherein the conductor is arranged between the first and the secondinsulator layer.
 60. Insulation element according to any one of theclaims 56-59, further comprising a measuring instrument arranged on orin the insulator sleeve.
 61. Insulation element according to theprevious claim, wherein the measuring instrument is configured totransmit a measured value wirelessly to a wireless receiver of amonitoring controller.